Google Search Appliance Upgrade and Migration Handbook - Manual (Page 18)

Single­node to Multi­node
When an architecture changes from a single GSA to multiple GSAs (eg. over 100M documents, requiring
two G500 appliances instead of one), Distributed Crawl and Serve will need to be configured. As a result, the
search index will either need to be re­indexed on the new architecture, or migrated. In this scenario, when
Distributed Crawl and Serve is enabled, the Master GSA node will distribute the index evenly across the
GSAs configured in the multi­node GSA network.
Multi­node to multi­node
When an existing Distributed Crawl and Serve architecture is modified (eg. using GB9009s and moving from
60M to 90M documents, requiring three GB9009 appliances instead of two), the new GSA can be added as
a new shard/node to the architecture, and the entire search index will be re­distributed evenly across all
GSAs. For example, if 54M documents have been indexed across two GSAs, and a third 30M GSA is
added to the network as a new shard, the index will be re­distributed and each GSA will have 18M docs.
Migrating with existing mirrored GSAs
The following scenarios describe detailed approaches to migrating to new search appliances where GSA
Mirroring is already in use on existing appliances.
Scenario A: New appliances are of the same model and software version
In a scenario where new appliances are of the same model and software version, mirroring can used to
migrate the index and configurations to a new appliance, which is then used as the master appliance of a
new GSA mirroring network. This scenario the same as that is described in the above section,
Migrating
search index and configurations .
Scenario B: New appliances are NOT of the same model and software version.
In a scenario where new appliances are not of the same model or software version, the recommended form
of GSA migration would be to migrate configurations only, and re­index all content on the new appliances.
However, if migration via mirroring is desired, and assuming that the new GSA model is compatible for
mirroring with the existing GSA model in use, an approach that could be taken would be to upgrade an
existing appliance (eg. backup replica appliance from the existing mirroring network), then mirror the
upgraded GSA to one of the new appliances, and use this GSA as a master in a new GSA mirroring
network. In this scenario, the following general steps would be taken:
1. Pause the crawl from the primary master appliance.
2. Remove a backup appliance from the existing mirroring network.
3. Upgrade this appliance to the same version as the new appliance(s).
4. Configure mirroring from this backup appliance to a new appliance, and complete the sync.
5. Disable mirroring between the backup appliance and the new appliance.
6. Configure mirroring on the new appliance to make it the primary master of a new mirroring
configuration.
7. Add additional new appliance(s) to the new mirroring network.
8. Cutover to new appliances and decommission old appliances.
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